radix tree test suite: add some more functionality

IDR needs more functionality from the kernel: kmalloc()/kfree(), and
xchg().

Link: http://lkml.kernel.org/r/1480369871-5271-67-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tools/testing/radix-tree/linux/slab.h

@@ -7,6 +7,9 @@
 #define SLAB_PANIC 2
 #define SLAB_RECLAIM_ACCOUNT    0x00020000UL            /* Objects are reclaimable */
 
+void *kmalloc(size_t size, gfp_t);
+void kfree(void *);
+
 struct kmem_cache {
 	int size;
 	void (*ctor)(void *);